A stabilizer for a vehicle needs to be disposed to extend in the right and left vehicle width direction while avoiding contact with auxiliary machinery, suspension parts, and so forth. For this reason, the stabilizer has a number of bending points to avoid contact with the other parts.
In a hollow stabilizer using a pipe (material), the material gathers (contracts) on the bend inner side of a bending point, and expands (extends) on the bend outer side of the bending point. Thus, the hollow stabilizer has been known to have a larger thickness on the bend inner side of the bending point and a smaller thickness on the bend outer side of the bending point than that of the material pipe before bending.
In addition, in the case where heat treatment of the stabilizer employs furnace heating of the entire part as heating for quenching, the inner side and the outer side of a bending point are heated to the same temperature. As a result, the difference in strength attributed to the difference in thickness remains as it is before the heat treatment.